US7235108B2 - Prosthesis liner or socket with a seal at the distal end - Google Patents

Abstract

A prosthetic liner for receiving a residual limb has a body with an open proximal end and a closed distal end. The liner includes a seal having an annular sealing lip positioned about the body axis on the body distal end. The sealing lip includes a root that is secured to the body distal end, and a sealing edge that extends from the root so as to form an opening and is biased away from the body distal end.

Description

BACKGROUND

A. Field of the Invention

This invention relates to prosthesis liner or socket having a seal at its distal end.

B. Related Art

With prostheses in general and leg prostheses in particular, a substantial effort is made to spread the retention force with which the prosthesis is attached to the involved residual limb over as large a surface as possible. So-called suction prostheses are especially advantageous in that respect, as they are sealed hermetically against the residual limb. When a force occurs tending to pull the prosthesis off the residual limb, a partial vacuum is produced which, in cooperation with the external atmospheric pressure, retains the prosthesis on the residual limb.

The suction socket presumes a positive air tight seal. When leaks arise, the partial vacuum at once disappears and the residual limb slips out of the socket.

It is clear on its face that such an event occuring with a leg prosthesis entails a dangerous fall. If the patient during walking loses the prosthesis, his/her step cannot be completed because the affected leg is suddenly shortened. Because walking/running is a dynamic process, the patient has no chance of stopping the step short.

Heretofore, one-hundred percent reliable air tight seals could not be assured. The residual limb volume changes with the patient's blood pressure, the temperature, and the like in such a way that a socket which is well-fitting and air tight one day may be poorly fitting and very loose another. The resulting consequence is the danger discussed above.

In order to safely preclude such danger, liners pulled over the residual limbs are used for prosthetic sockets, even those that are for above-knee use. At its distal end the liner is fitted with a locking adapter engaging a detent mechanism or the like of the prosthetic socket. In this configuration the liner is seated in an air tight manner on the residual limb and there is no danger of the residual limb slipping out of the liner. Moreover, on account of its intrinsic prestressing force, the liner is frictionally held against the residual limb. On the other hand the liner's elasticity results in strong narrowing at its distal end when tension is introduced at such end through the locking adapter. The result is a so-called milking effect.

It is important for comfort during wearing that the residual limb not be compressed when a tension is applied to the distal end. Such objective may be assured when the liner is inserted in the hard prosthetic socket in an air tight condition and is kept there by means of a partial vacuum.

Accordingly, those embodiments which involve both mechanical and hermetic attachment will be advantageous.

In another example, the liner should include assistance for inserting the liner into a socket. For that purpose the liner is fitted at its distal end with a cord which initially is threaded through an aperture at the prosthetic socket distal end. The patient forcefully pulls the cord through the aperture, such that the residual limb, seated in the liner, is pulled into the prosthetic socket. Thereupon the cord is secured on the outside of the prosthetic socket. In this kind of prosthesis, the prosthetic socket is retained against the residual limb substantially by friction in relation to the cord affixed on the outside of the prosthetic socket.

BRIEF SUMMARY OF THE INVENTION

As compared to the above discussed state of the art, the objective of the present invention is to create a prosthetic socket assuring reliable retention by partial vacuum even when the prosthetic socket has openings at its distal end.

Another objective of the present invention is to create a residual limb liner which is fitted with a locking adapter or a cord and which nevertheless can be held firmly in the prosthetic socket by partial vacuum.

All prosthetic sockets fitted with additional mechanical liner locks share the characteristic of a more or less air leakage through larger or smaller openings in the distal end of the socket. Air can move through these openings into the prosthetic socket into the gap between the socket's inside wall and the liner. If so, the partial vacuum then collapses and the prosthetic socket can hardly be retained on the liner. To prevent such leakages, all embodiments of the present invention provide a substantially annular seal fitted with a sealing lip running around the opening. The sealing lip subtends a sealing edge that is nearer the opening than its root.

Depending on the type of embodiment involved, the seal may be affixed by its root to the prosthetic socket's inner side, or it may be affixed to the outside of the liner at the locking adapter.

When the prosthetic socket is loaded in tension, external air flows through the prosthetic socket aperture into the gap between the liner and socket. As a result a pressure gradient is created at the sealing edge that will compress the edge ever more strongly against the liner or the prosthetic socket the greater the differential is between the pressure in the prosthetic socket's gap and the external atmospheric pressure. Sealing may always be assured even when initially the sealing edge rests by means of a small prestressing force against the respective opposed surface, namely the liner or the prosthetic socket, depending on where the seal is not hermetically sealed at its root.

If the prosthetic socket is fitted with an annular, disk type seal the root of which is integral, air tight bonded with the socket, various types of liners may be used. Liners may be used wherein a cord is provided at their distal end that is pulled through the opening, and liners may be used which are designed with rigid locking adapters using pins or the like. The seal may be selected to be of very large diameter, so that the danger of damaging the sealing lip by the pin of the locking adapter is precluded. Again, strong prestressing of the seal, sometimes found in the prior art, is not required.

Accordingly the seal in the prosthetic socket offers long service life and also is very reliable compared to O-rings that rest against the smooth part of the pin-shaped locking adapter. The air tightness of such O-rings actually cannot be tested and each time the locking adapter is inserted through the O-rings, they are degraded another bit.

Another approach is to fit the seal with a further sealing edge, both sealing edges then being situated on the same side of the annular root relative to the radial direction of the root. Such a seal is appropriate for retrofitting combinations of liner and prosthetic socket and using pin type locks. The seal may be affixed to the pin and will seal it by a sealing edge. The seal remains on the pin and need not be pierced when the patient enters the prosthetic socket. In this manner any danger of damaging the other sealing edge when the patient enters the prosthetic socket of the invention is precluded.

The basic principle of the present invention also may be applied to liners. In this case the seal is affixed by its root to the liner outer side, and the sealing edge, as before, extends toward the aperture. In this design the sealing edge seals off the aperture at the smooth inner side of the prosthetic socket. Lastly, the basic concept of the invention may be applied to those liners with a cord that is pulled through a prosthetic socket aperture, such liners initially primarily acting as slip-in aids. Said lip in this design even may be made integral with the liner or it may be retro-attached onto the liner.

The last-mentioned approach is especially suitable when replacing prosthetic sockets lacking a seal and liners fitted with draw cords.

It may be appropriate as regards all embodiments to use spacers to ensure the sealing lip rests securely against the surface to be sealed off and from which it will separated when the prosthesis is removed, while involving a low prestressing force. Accordingly the spacers are situated between the sealing lip and the surface to which the root is attached.

Further refinements of the present invention are the objects of the dependent claims. Even those combinations of features that are not explicitly illustrated in discussions of the exemplary embodiments should be construed as being claimed.

DESCRIPTION OF THE DRAWINGS

The drawing shows illustrative embodiments of the present invention.

FIG. 1 is a longitudinal section of a residual limb fitted with a liner of the invention operating with a prosthetic socket,

FIG. 2 is an enlarged detail of the distal end of the liner ofFIG. 1,

FIG. 3 is another embodiment of a seal for the liners ofFIGS. 1 and 2,

FIG. 4 is a longitudinal section of a prosthetic socket of the invention for a liner with a locking adapter,

FIG. 5 is a longitudinal section of a liner having a cord for drawing it into a prosthetic socket, and

FIG. 6 is a prosthetic socket for the liner ofFIG. 5.

DETAILED DESCRIPTION

In highly schematic form, and as an example of the present invention,FIG. 1 shows aprosthetic socket1 for use above-the-knee, into which an amputationresidual limb2 onto which aliner3 was donned has been received.

Theprosthetic socket1 has a cup-shape configuration comprising alateral wall4 subtending anopening5 at its proximal end and being closed by an inverted dome-like base6 at its distal end. Thewall4 and thebase6 merge integrally into each other and define a correspondinginner volume7 that receives the amputationresidual limb2.

At its lower end, thebase6 is integrally extended by acylindrical fitting8 connected to anartificial knee9.

A two-part lock11 assures reliable and mechanical retention of theliner3 in theprosthetic socket1. Thelock11 is fitted with acylindrical borehole12 which is located in thecylindrical extension8 and which at its upper end and through a conically widening opens into theinner volume7 of theprosthetic socket1. Apassage13 runs transversely to thecylindrical borehole12 and receives a longitudinallydisplaceable slider14. Thepassage13 runs transversely to the longitudinal axis of theborehole12 and as a result theslider14 is guided transversely, or radially, relative to theborehole12. Theslider14 includes anaperture16 which is fitted on an edge opposite thedrive knob17 with adetent edge18. Theslider14 is biased by ahelical compression spring19 toward thedrive knob17.

Using stop elements (omitted), theslider14 can only be advanced a given distance by thehelical compression spring19 toward thedrive knob17. Moreover the stop element (omitted) assures that adequate free space shall remain between the edge of thetooth18 and the opposite wall of thecylindrical borehole12.

The liner is a sock-like or pouch-like structure made of an air-impermeable, skin-compatible material such as silicone, having a reinforcedbase21 at its distal end. An umbrella-shapedlocking element22 is anchored in thebase21 and constitutes the other part of the lockingadapter11.

The lockingelement22 comprises anenlarged head23 molded into the base21 as shown. Thehead23 is fitted with acylindrical pin24 which is smooth in itssegment25 directly adjoining thehead23. Thepin24 is fitted with circumferentially symmetricalserrated teeth26 at a distance located away from thehead23, said teeth comprising of a plurality of annular adjacent grooves extending along thepin24. The shapes of theserrated teeth26 match that of thedetent edge18 and as a result the detent connection described below may take place. Moreover the diameter of thepin24, i.e. its tapered free end, is selected in such a way that without interference from theslider14, thepin24 can be inserted through theborehole12 and through theaperture16 of theslider14.

As shown in the enlargement ofFIG. 2, aseal27 is configured on the outside of thebase21. Theseal27 is an elastomeric, substantiallycircular sealing lip28. The sealinglip28 subtends aroot29 and a sealingedge30. Theroot29 is illustratively bonded in an air tight manner to the outside of thebase21. From there the sealinglip28 projects radially with its sealingedge30 extending toward the lockingpin24. The sealingedge30 closes on itself and defines an aperture having a diameter of about 15 to 60 mm, as a result of which theshank24 is surrounded in all directions by the sealing edge with radial play.

With the use of anannular foam insert31, the sealingedge30 is biased a slight distance away from the outside of thebase21. Thefoam insert31 is open cell and situated in the gap between the sealing lip and the outside of thebase21.

The configuration discussed above operates as follows:

When the user wants to wear the prosthetic socket and affix it to hisresidual limb2, he first will don theliner3. Upon full insertion into the liner, the end of theresidual limb2 rests against the inside of thebase21. The lockingpin24 then extends in the axial direction of theresidual limb2. Next, with thepin24 in front, the patient inserts theresidual limb2 into theprosthetic socket1. During this insertion, thecylindrical pin24 is trapped by the conical, upper portion of theborehole12 and is then guided into theborehole12. During further insertion of theresidual limb2 into theprosthetic socket1, thepin24 by its circumferentially symmetricalserrated teeth26 penetrate and pass through theaperture16 of theslider14.

Theprosthetic socket1 will be fully in place as soon as thebase21 of theliner3 rests on the inside of thebase6 of theprosthetic socket1. In this condition the sealingedge29 hermetically rests against the opposite smooth inner side of theprosthetic socket1. At the same time thepin24 shall be locked withslider14 by a corresponding mutual engagement.

If during this operational condition a tension is exerted on theprosthetic socket1 and axial play exists between theslider14 and aserration26, then it will be nevertheless impossible to pull theprosthetic socket1 off theresidual limb2. As long as the tension is applied, external, atmospheric air will flow through the borehole12 or theguide duct13 intoinside volume7 of theprosthetic socket1. This air reaches the conical gap between the sealinglip28 and the outside of thebase21 of theliner3. This air increases the pressure at which the sealingedge30 is forced against the inside of theprosthetic socket1, thus strengthening sealing. Due to the sealingedge30, the air is impeded from penetrating the gap between theliner3 and theprosthetic socket1 beyond the sealinglip28. The above-kneeresidual limb2 jointly with its donnedliner3 is retained in place independently of thelocking device11 in theprosthetic socket1.

The above discussion assumes that theresidual limb2 is seated in sealed manner in thesocket1 at the proximal end. If it were otherwise, an additional and corresponding seal must be provided—which however is not an object of the present invention.

The initially mentioned milking effect cannot occur. Theresidual limb2 is held in a dimensionally stable manner within the rigidprosthetic socket1. No tension forces are transmitted through thepin24 into thebase21 of theliner3 that might cause narrowing of theliner3.

In order to reliably preclude such force transmittal through thepin24, theserrations26 may be provided at the tip area only of thepin24 and the pin segment above may merge into a smooth zone of lesser diameter before reaching thesection25. In this manner thepin24 would be provided with a commensurate axial play in theslider14 and would not impede the locking of theprosthetic socket1 by means of partial vacuum. With such a design of thepin24, the partial vacuum would become effective first, before theliner3 might distend due to a force transmitted through thepin24.

It is easily seen that the sealinglip28 is directed in such a way that the pressure gradient generated when tension is exerted on theprosthetic socket1 increasingly compresses the sealinglip28 against theprosthetic socket1 the greater the tension and that the partial vacuum would be exerted on the other side of the sealinglip28.

In order that enough prestressing force be present from the beginning and to assure that the external atmospheric pressure may attain the self-reinforcing compression effect level, use is made of afoam ring31, which is open-cell.

To allow removing theresidual limb2 out of theprosthetic socket1, the user opens a valve in thesocket1 to let air flow into theinside space7 while bypassing theseal27. After pressing theactuator knob17, the snap-inserration26 is released and the residual limb then may be pulled out of theprosthetic socket1 jointly with theliner3.

Instead of using a flat element as aseal27 inFIG. 2 that is bonded at itsroot29 to the outside of theliner3, theseal27 may be configured as shown inFIG. 3.

The seal ofFIG. 3 extends beyond theroot29 into a further sealinglip35 tubularly folding on itself and defining another sealing edge at36. The twosealing edges30 and36 are situated on the same side relative to theroot29 and are located radially relative to an axis passing through the circles defined by the two sealingedges30 and36. Theseal27 ofFIG. 3 is pulled on thepin24 and by its sealingedge36 seals off the smooth,cylindrical segment25 of theshank24. Operation of theseal27 otherwise is as fully described above.

Theseal27 is easily applicable for retrofitting existing liner systems.

FIG. 4 shows an embodiment wherein theseal27 is adhesively bonded onto aprosthetic socket1. The geometry of theprosthetic socket1 ofFIG. 4 is identical with that shown inFIG. 1. The liner used in the latter case also is identical with theliner3 discussed in relation toFIGS. 1 and 2, except that theseal27 is not bonded to theliner3. Theannular seal27 instead is hermetically affixed, for instance adhesively, by itsroot29 to the inside of theprosthetic socket1, the sealingedge30 in this manner defining an aperture concentric with theborehole12.

Because of the curvature of thebase6 of thesocket1, theseal27 by its sealingedge30 will be raised off the inside of thesocket1.

Theseal27 otherwise operates as described above.

FIG. 5 shows aliner3 which is fitted at its distal end with acord37. Again, anannular seal27 similar to that ofFIG. 2 is adhesively bonded to the outside of thedistal base23 of theliner3. Theliner3 ofFIG. 5 is used with a prosthetic socket such as shown inFIG. 6.

Theprosthetic socket1 ofFIG. 6 is fitted at its distal end with anaperture38 through which thecord37 extends.

When putting on theprosthesis1, thecord37 is threaded through theaperture38. Thecord37 is pulled to assist in inserting theresidual limb2 into theprosthetic socket1. When fully installed, the sealingedge30—as already discussed above—will rest against the inside of theprosthetic socket1. As a result and on account of the partial vacuum, theprosthetic socket1 is affixed against the outside of theliner3. Moreover, for mechanical securing, thecord37 is anchored on a hook (omitted) at the outside of theprosthetic socket1.

Instead of mounting theseal27 on the outer side of theliner3 as shown inFIG. 5, it may also be mounted, as shown inFIG. 6, on the inner side of theprosthetic socket1. Said seal then is configured concentrically with theaperture38, itsroot29 being adhesively bonded to the inner side of theprosthetic socket1.

Lastly, aseal27 on theliner3 as shown inFIG. 5 may be combined with aseal27 on the inside of theprosthetic socket1 as shown inFIG. 6. With the patient wearing theprosthetic socket1, twoseals26 would be directly superposed at their sealing edges30.

The last-cited embodiment is especially appropriate for retrofitting when theprosthetic socket1 on account of manufacturing methods does not subtend a sufficiently smooth surface in the vicinity around theaperture38 that would be suitable for sealing using the sealingedge30.

FIGS. 2 and 5 are based on the assumption that the sealinglip28 was manufactured as a separate part. However it is quite clear that the sealinglip28 also may be an integral part of theliner3 on the outer side of same.

The shown above-knee socket serves merely an exemplary purpose. The invention is applicable to all kinds of prosthetic sockets such as below-knee and arm prostheses.

Summarizing, a prosthetic socket having an aperture at the distal end is fitted with a seal which is configured in a manner such that applying a tension to the prosthetic socket generates a self generating force at said seal, wherein the external atmospheric pressure increasingly compresses the seal through a sealing lip. The seal may be affixed to the prosthetic socket and/or to the liner, with the sealing edge always nearer the aperture to be sealed off than is the root of the sealing lip.

Claims (12)

1. A prosthetic liner for receiving a residual limb, the liner having a body with an open proximal end and a closed distal end, and an axis, the liner comprising:

at least one seal having an annular sealing lip positioned about the body axis on the body distal end, the sealing lip including a root secured to the body distal end, and a sealing edge extending from the root towards the body axis, the sealing edge being biased away from the body distal end and forming an opening about the body axis.

2. The prosthetic liner according toclaim 1, wherein the seal is configured as a disc-like annulus.

3. The prosthetic liner according toclaim 1, wherein the seal is hermetically and adhesively bonded at the root to the liner body.

4. The prosthetic liner according toclaim 1, wherein a compressible insert is provided between body distal end and the sealing edge.

5. The prosthetic liner according toclaim 4, wherein the compressible insert is an open-pore foam or a spring.

6. The prosthetic liner according toclaim 1, further comprising a locking element secured to the liner distal end and positioned along the body axis, the seal opening surrounding and radially spaced from the locking element.

7. The prosthetic liner according toclaim 6, wherein the locking element is a pin having a serrated portion.

8. A prosthetic liner for receiving a residual limb, the liner having a body with an open proximal end and a closed distal end, and an axis, the liner comprising:

at least one seal having an annular sealing lip positioned about the body axis on the body distal end, the sealing lip including a root secured to the body distal end, a first sealing edge extending from the root towards the body axis, and a second sealing edge extending from the root towards the body axis, the second sealing edge positioned more proximate to the liner distal end than the first sealing edge, the first and second sealing edges being biased away from the body distal end and forming an opening about the body axis.

9. The prosthetic liner according toclaim 8, wherein the first and second edges are elastically maintained apart.

10. A prosthetic liner for receiving a residual limb, the liner having a body with an open proximal end and a closed distal end, the liner comprising:

at least one seal having an annular sealing lip positioned obliquely relative to the body axis on the body distal end, the sealing lip including a root secured to the body distal end, and a sealing edge extending from the root, the sealing edge biased away from the body distal end and forming an opening.

11. The prosthetic liner according toclaim 10, further comprising a locking element secured to the liner distal end, the seal opening surrounding and radially spaced from the locking element.

12. The prosthetic liner according toclaim 11, wherein the locking element is an elongate cord.

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